In its present form--it is on exhibition at the Engineers Club in Dayton, Ohio--the _No. 3_ engine embodies one feature which became standard construction on all the Wright 4-cylinder models. This was the addition of a number of holes in a line part way around the circumference of the cylinder barrel so that they were uncovered by the piston at the end of its stroke toward the shaft, thus becoming exhaust ports (see Figure 9). This arrangement, although not entirely novel, was just beginning to come into use, and in its original form the ports exhausted into a separate chamber, which in turn was evacuated by means of a mechanically operated valve, so that two exhaust valves were needed per cylinder. Elimination of this chamber and the valve arrangement is typical of the Wrights' simplifying procedure, and it would seem that they were among the very first to use this form.[14] [Footnote 14: Rankin Kennedy, _Flying Machines--Practice and Design_, 1909.] The primary purpose of the scheme was to reduce, by this early release and consequent pressure and temperature drop, the temperature of the exhaust gases passing the exhaust valve, this valve being one of their main sources of mechanical trouble. It is probable that with the automatic intake valves being used there was also a slight effect in the direction of increasing the inlet charge, although with the small area of the ports and the short time of opening, the amount of this was certainly minor. With the original one-piece crankcase and cylinder jacket construction, the incorporation of this auxiliary porting was not easy, but this difficulty was overcome in the development engine by making different castings for the crankcase itself and for the cylinder jacket and separating them by several inches, so that room was provided between the two for the ports. This engine demonstrated the most power of any of the flat 4s, eventually reaching an output of approximately 25 hp, which was even somewhat more than that developed by the slightly larger 4-1/8-in.-bore flight engine, with which 21 hp was not exceeded. Indicative of the development that had taken place, the performance of the _No. 3_ engine was twice the utilized output of the original engine of the same size, an increase that was accomplished in a period of less than three years.